When a lost part of a tooth is filled or covered with a restorative material, generally a dental adhesive is used. When such a dental adhesive is allowed to act on a tooth structure, particularly on dentin, it is important for the dental adhesive to have an decalcifying effect that allows a dentin surface to be dissolved with an acidic component, a penetration effect that allows a monomer component to penetrate into a collagen layer of the dentin, and a curing effect that allows the monomer component thus penetrated to solidify to form a hybrid layer (hereinafter also referred to as a “resin-impregnated layer”) with collagen.
It has been studied so far to simplify the form of application of the dental adhesive from a three-component three-step type in which the aforementioned decalcifying effect, penetration effect, and curing effect are applied sequentially, to a two-component two-step type in which the decalcifying effect and the penetration effect are integrated, and further to a one-part one-step type in which the decalcifying effect, penetration effect, and curing effect are all combined together. Particularly in recent years, developments have progressed on the one-part one-step dental adhesive that makes the bonding work easy and fast and that is resistant to contamination by saliva and blood.
For example, Patent Literature 1 discloses a one-part dental adhesive composition including a hydrophobic polymerizable monomer having an acidic group, a water-soluble polymerizable monomer, water, a photopolymerization initiator, aromatic tertiary amine having an electron-withdrawing group, a crosslinkable polymerizable monomer, and a basic compound for producing a water-soluble salt through a reaction with a part of the hydrophobic polymerizable monomer having an acidic group. According to Patent Literature 1, it is possible to obtain a composition that can achieve high adhesive property even when no pretreatment is applied to the tooth structure, and that also has excellent storage stability. However, although having excellent initial adhesive property, this dental adhesive composition may cause an adhesive layer and a resin-impregnated layer to be degraded because of water absorption. Thus, its long-term bond durability is left to be improved.
As an adhesive composition that exhibits excellent adhesive property over a long period of time, Patent Literature 2 discloses an adhesive composition for a biomaterial, including a polymerizable monomer having a fluorocarbon group. The literature describes that a cured product obtained by polymerizing a polymerizable monomer having a fluorocarbon group has excellent water absorption rate and dimensional stability. It further describes that a mixed composition of polymer powder obtained by polymerizing a polymerizable monomer having a fluorocarbon group, a polymerizable monomer having a fluorocarbon group, a polymerizable monomer having an acidic group, and a polymerization initiator has excellent adhesive property to a tooth structure.
As a dental composition including a polymerizable monomer having a fluorocarbon group, Patent Literature 3 discloses a composition including a polymerizable monomer having a fluorocarbon group and at least two polymerizable groups, a hydrophilic polymerizable monomer, and a polymerization initiator. The literature describes that this composition can be cured through polymerization in a short period of time, and has satisfactory affinity to a tooth structure and an adhesive material while exhibiting excellent water repellence and coloration resistance, and excellent adhesive property can be achieved.